1. Field of Application
The present invention relates to a drive circuit incorporating an integrated circuit, for driving a voltage-controlled type of switching device. The invention further relates to a method of manufacturing such a drive circuit.
2. Description of Related Art
A type of drive circuit is known, for example as described in Japanese patent publication No. 2009-11049, for driving a voltage-controlled switching device such as an insulated-gate type of transistor, in which the drive circuit includes a stabilized-current circuit for supplying a constant current as a charging current to a control terminal (e.g., gate) of the driven switching device. The term “charging” is used here in a general sense, for referring to a charging current (positive-direction current) for increasing an amount of positive charge or a discharging current (negative-direction current) for decreasing an amount of positive charge. In recent years, as integrated circuits have become increasingly more compact and lower in cost, it has become possible to incorporate the functions of such a drive circuit in an integrated circuit. In that case, it is necessary that the required level of charging current (determined by the switching speed of the driven switching device) is within the supply current rating of the integrated circuit. It is also necessary to limit the switching frequency such that the rated maximum operating temperature of the integrated circuit is not exceeded.
Hence in the prior art, for wide applicability, it has been necessary for such an integrated circuit to be capable of providing the highest drive current that might be required from the drive circuit, and capable of operating at the highest switching frequency that might be required.
Thus, obtaining such generality of manufacture will result in the integrated circuit being large in scale and expensive to manufacture, and having capabilities which are excessive in relation to usual application requirements, since only a small proportion of such drive circuits must drive switching devices having an extremely high switching speed or operating at an extremely high switching frequency.